package com.zcsy.commons.util;

import java.io.IOException;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

public class DESEncryption {

    private final static String DES = "DES";

    public static void main(String[] args) throws Exception {
	String data = "123456";
	String key = "tanghan";
	System.err.println(encrypt(data, key));
	System.err.println(decrypt(encrypt(data, key), key));

    }

    /**
     * Description 根据键值进行加密
     * 
     * @param data
     * @param key
     *            加密键byte数组
     * @return
     * @throws Exception
     */
    public static String encrypt(String data, String key) throws Exception {
	String entryKey = getEncryKey(key);
	byte[] bt = encrypt(data.getBytes(), entryKey.getBytes());
	String strs = new BASE64Encoder().encode(bt);
	return strs;
    }

    /**
     * Description 根据键值进行解密
     * 
     * @param data
     * @param key
     *            加密键byte数组
     * @return
     * @throws IOException
     * @throws Exception
     */
    public static String decrypt(String data, String key) throws IOException,
	    Exception {
	if (data == null)
	    return null;
	String entryKey = getEncryKey(key);
	BASE64Decoder decoder = new BASE64Decoder();
	byte[] buf = decoder.decodeBuffer(data);
	byte[] bt = decrypt(buf, entryKey.getBytes());
	return new String(bt);
    }

    /**
     * Description 根据键值进行加密
     * 
     * @param data
     * @param key
     *            加密键byte数组
     * @return
     * @throws Exception
     */
    private static byte[] encrypt(byte[] data, byte[] key) throws Exception {
	// 生成一个可信任的随机数源
	SecureRandom sr = new SecureRandom();

	// 从原始密钥数据创建DESKeySpec对象
	DESKeySpec dks = new DESKeySpec(key);

	// 创建一个密钥工厂，然后用它把DESKeySpec转换成SecretKey对象
	SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);
	SecretKey securekey = keyFactory.generateSecret(dks);

	// Cipher对象实际完成加密操作
	Cipher cipher = Cipher.getInstance(DES);

	// 用密钥初始化Cipher对象
	cipher.init(Cipher.ENCRYPT_MODE, securekey, sr);

	return cipher.doFinal(data);
    }

    /**
     * Description 根据键值进行解密
     * 
     * @param data
     * @param key
     *            加密键byte数组
     * @return
     * @throws Exception
     */
    private static byte[] decrypt(byte[] data, byte[] key) throws Exception {
	// 生成一个可信任的随机数源
	SecureRandom sr = new SecureRandom();

	// 从原始密钥数据创建DESKeySpec对象
	DESKeySpec dks = new DESKeySpec(key);

	// 创建一个密钥工厂，然后用它把DESKeySpec转换成SecretKey对象
	SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);
	SecretKey securekey = keyFactory.generateSecret(dks);

	// Cipher对象实际完成解密操作
	Cipher cipher = Cipher.getInstance(DES);

	// 用密钥初始化Cipher对象
	cipher.init(Cipher.DECRYPT_MODE, securekey, sr);

	return cipher.doFinal(data);
    }

    private static String getEncryKey(String key) {
	String encryptKey = key;
	int enkeyLen = 8;
	int keyLen = key.length();

	if (keyLen > enkeyLen) {
	    encryptKey = encryptKey.substring(0, 8);
	} else {
	    int paddLen = enkeyLen - keyLen;
	    for (int i = 0; i < paddLen; i++) {
		encryptKey += "0";
	    }
	}
	return encryptKey;
    }

}
